Boston Bomb Survivor Seeks 'Guardian Angel' Who Saved Her Life

"It's tough and it's going to kind of suck," McMahon told Sdoia. "[But] I can tell you're tough so I'm sure you'll be great through it."

Offering words of support and advice on possible prosthetics, McMahon said she hopes to be a friend to those like Sdoia facing a new reality.

"It puts a smile on someone's face to see, 'Wow she's dealing with something that I'm going through right now,'" McMahon said. "It's not over. You may not be able to do the things you used to do, the exact same way. But there are still things you can do."

Sdoia too finds comfort in meeting McMahon and other amputees.

"I'm taking all of this information into my head and hoping that moving forward, knowing what they have done, will propel me to do what I want to do," Sdoia said. "When there's a tragedy like this, it does nothing but bring people together."

Watch Roseann Sdoia and Bree McMahon's story on "20/20: In an Instant" tonight at 10 ET.